Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.72	5.365%	$97.6944	$97.69	$97.70	$97.70
Purchase #2	$40.89	8.524%	$44.3755	$44.38	$44.40	$44.40
Purchase #3	$195.76	13.704%	$222.587	$222.59	$222.60	$222.60
Purchase #4	$86.67	4.565%	$90.6265	$90.63	$90.65	$90.60
Purchase #5	$228.53	4.350%	$238.4711	$238.47	$238.45	$238.50
Purchase #6	$7.36	3.476%	$7.6158	$7.62	$7.60	$7.60
Purchase #7	$211.46	7.170%	$226.6217	$226.62	$226.60	$226.60
7 purchase totals =	$863.39		$927.9920	$928.00	$928.00	$928.00